FR-A-2810314 describes a rapid binder for self-compacting concrete comprising Portland cement, calcium aluminate, calcium sulfate, an accelerator, a retarder and a superplasticizer of the polyphosphonate-polyox type. In that document, it is indicated that this binder makes it possible to achieve a workability of longer than 1 hour, and to pump the concrete thanks to this self-compacting formulation, while still having a high compressive strength at 6 hours and at 24 hours, including at temperatures between 10° C. and 35° C. The applications described in that document are the emergency repair of structures and the temporary support for tunnels, galleries or other similar structures. There is no mention of concrete shell applications.
U.S. Pat. No. 3,427,175 describes compositions comprising an accelerator system containing a calcium nitrite. This document also describes a cure at a temperature that is not compatible with the outdoor temperatures conventionally encountered on building sites.
JP-A-2000281412 describes accelerator systems containing a calcium salt, which is calcium sulfite or sulfate, in combination with an organic adjuvant and a superplasticizer. It is indicated that compressive strength is obtained in a relatively short time, but the data provided are only data obtained at 24 hours.
GB-A-2033367 and GB-A-2058037 describe accelerator systems comprising a calcium aluminate mixed with calcium sulfate, a hydroxyacid (for example citric acid) and an inorganic salt (for example a nitrite or nitrate, sodium carbonate being indicated as preferred).
EP-A-537872 describes an accelerator system comprising a nitrite or nitrate, for example calcium nitrite or nitrate, combined with a specific copolymer superplasticizer.
A few commercial products are also known. Products from SIKA, in particular Sikaprise SC2, containing calcium nitrate, sodium thiocyanate and formaldehyde, may be mentioned. Products from GRACE, in particular Polarset, containing calcium nitrite, calcium nitrate (and bromide salts), a small amount of thiocyanate and methyldiethanolamine, may also be mentioned. Products from MBT, especially combination products, accelerator Pozzolith NC 534, high water-reducing superplasticizer Glenium 3030 and retarder Delvo, may also be mentioned.
US 20030127026 (U.S. Pat. No. 6,858,074) describes an accelerator system comprising, in combination: a polycarboxylate-type superplasticizer, an accelerator and a retarder. The accelerator may be chosen in particular from alkaline-earth metal nitrites, thiocyanates, halides, salts, especially calcium salts of acids, for example formic acid, etc. It does not describe mixing these components. One retarder is in particular a carboxylic acid. The flexural strength is indicated as being at least 2.8 MPa and the compressive strength as being at least 15 MPa, in a time of 4 hours after pouring, at a temperature of between 10° C. and 38° C.
The cementious compositions according to this invention have a workability retention time limited to a maximum of 30 minutes, a high cement content and low water/cement ratios, of between 0.25 and 0.40.
US 20040149174 describes a system similar to the one which is the subject of the preceding application, but in combination with a salt for lowering the freezing point of the mix. Combinations of a polycarboxylate-type superplasticizer, of a freezing-point-lowering salt (alkaline-earth metal nitrites are mentioned), of an accelerator (thiocyanates and halides are mentioned) and of a retarder (carboxylic acids are mentioned) are claimed. The examples do not specify the precise compounds used, nor do they provide information about the workability retention and the mechanical strength obtained at 4 or 6 hours. They relate to concretes that are not fluid or self-compacting concretes. The properties were studied at temperatures which in certain cases were around −1° C.
However, there is still a need for a method of manufacturing concrete components and structures using rapid binder compositions, having a long workability retention, resulting in short-term mechanical strength being rapidly achieved even at temperatures below 10° C., and thus making it possible to increase the rate at which formwork can be reutilized.